In the existing communication network, no matter it is fixed communication network, Global System for Mobile communication (GSM) network or Code Division Multiple Access (CDMA) mobile communication network, when a called party receives an incoming call from a calling party, the called party may select to or not to answer the call, or even to reject the call (the called party may reject an incoming call by pressing the call-termination key). We may often encounter such a case that the called party is busy when an incoming call arrives; for example, the called party is busy answering another important call, or dealing with an important affair, or is in a meeting. In this case, the called party usually rejects the call, and the Terminating Mobile Switching Center (T_MSC) in the prior art plays an invariable prompt tone, such as “The subscriber you dialed cannot be connected for the moment” or “The subscriber you dialed is busy now”, to the calling party.
If it is the first time that the calling party encounters such a case, he/she may take it for granted as indicated by the prompt tone that the called party cannot be connected or the called party is busy. However, as time passes, all people know that the occurrence of such a prompt tone results from the called party's rejection of the call. Moreover, before the called party rejects the call, the calling party may hear a ringback tone which indicates that the called party is in idle state. In practice, it is considered as impolite to reject a call and this may affect the relationship between the calling and called parties. Even if the called party calls back to the calling party for explanation after the event, the effect may be imperfect due to untimeliness.
Additionally, in the prior art, there also exists a technical solution for a user to customize a ringback tone. In other words, after a called party subscribes to a ringback tone service, when a calling terminal calls the called terminal and the called party is in idle state, a Ringback Tone Server (RBTS) sends a ringback tone customized by the called party to the calling party. Here, the called party may customize different ringback tones according to individual tastes, or according to calling numbers or according to time. Thus, the individualized requirements of the user may be met to a certain degree. However, these ringback tones are precustomized, so different ringback tones cannot be sent in real time according to the actual situation to meet the requirements of the terminal user flexibly.